The closing devices which are more particularly concerned by this process are those constituted by a tapped closing device extended in its lower part by a tamper-proof ring joined to the closing device by a breakable connection zone; this ring comprising an annular joining strip with controlled deformation, defined on the one hand, in the lower part, by an inner annular projection whose upper face is substantially perpendicular to the axis of the device and whose lower face is inclined by an acute angle with respect to said axis and, on the other hand, in its upper part, by an outer annular projection.
These devices have in particular formed the subject matter of Applicants' International Patent Applications PCT/FR94/00145 and PCT/FR94/00144.
The processes for manufacturing such devices generally comprise moulding by injection or compression, demoulding, then an ejection of the device parallel to its axis as described in International Patent Application No. PCT/FR94/00144.
During packaging, when the device is first screwed on the flanged container, after having been filled, it is necessary to exert a tightening torque to effect a controlled deformation of the joining strip and to connect the device by clipping the inner annular projection beneath the flange.
Now, the wider the inner projection, the thicker the joining strip and the more the tamper-proof ring is rigid, this strengthening the degree of impregnability.
However, the tightening torque then becomes relatively considerable, as well as the unscrewing torque which largely depends thereon, which constitutes a drawback for the consumer.
Consequently, the technical problem resides in the search for a satisfactory compromise between an easy unscrewing (which depends mainly on the initial tightening torque) and a high degree of impregnability.
It is an object of the present invention to overcome this problem satisfactorily.